Wednesday, May 02, 2018

The Aurora and The Sunrise | International Space Station



"Sunrise crashes an aurora party over the southern hemisphere," said NASA astronaut Ricky Arnold of this image he snapped from the International Space Station.

Auroras are one of the many Earthly phenomena the crew of the space station observe from their perch high above the planet. The dancing lights of auroras provide spectacular views, but also capture the imagination of scientists who study incoming energy and particles from our Sun. Auroras are one effect of such energetic particles, which can speed out from the Sun both in a steady stream called the solar wind or from giant eruptions known as coronal mass ejections or CMEs. After a trip toward Earth that can last three days, the solar particles and magnetic fields cause the release of particles already trapped near Earth, which in turn trigger reactions in the upper atmosphere in which oxygen and nitrogen molecules release photons of light. The result: the Northern and Southern lights.

On the International Space Station (ISS), you can only admire an aurora until the sun rises. Then the background Earth becomes too bright. Unfortunately, after sunset, the rapid orbit of the ISS around the Earth means that sunrise is usually less than 47 minutes away.

In this image, a green aurora is visible below the ISS—and on the horizon to the upper right, while sunrise approaches ominously from the upper left. Watching an aurora from space can be mesmerizing as its changing shape has been compared to a giant green amoeba. Auroras are composed of energetic electrons and protons from the Sun that impact the Earth's magnetic field and then spiral down toward the Earth so fast that they cause atmospheric atoms and molecules to glow. The ISS orbits at nearly the same height as auroras, many times flying right through an aurora's thin upper layers, an event that neither harms astronauts nor changes the shape of the aurora.

Image Credit: NASA, Astronaut Ricky Arnold, Expedition 55
Release Date: April 11, 2018


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